1. Field of the Invention
The invention relates to printed circuit board plating operations, and more particularly, to a continuous, computer controlled printed circuit board plating system.
2. History of the Prior Art
In the past, printed circuit board plating operations have included a necessity for placing a plurality of individual printed circuit boards onto a rack and then manually moving the rack through various cleaning tanks and plating tanks in a manner so as to produce uniformly controlled thickness of plating on the boards in a desired pattern. Such operations are relatively unautomated in the sense that an operator is used to both load and unload the racks as well as to time and move the racks from tank to tank in order to ensure a controlled thickness of copper both within holes formed through the boards and upon the surface of the boards themselves.
Improved printed circuit board plating operations have included computer controlled movement of racks from tank to tank. That is, the tank withdrawal operator is replaced by a timing mechanism which precisely measures the amount of time that the boards have been in a particular tank and withdraws the rack whenever a desired thickness of copper has been placed upon the boards. Such computer control devices still require operator monitoring to physically load and transfer the racks of printed circuit boards from tank to tank following the automatic withdrawal from the previous tank based upon a computer controlled timing circuit.
Additionally, prior art printed circuit board plated operations have been inherently wet, messy, and odoriferous. Such operations have also been characterized by the discharge of substantial quantities of vaporous and liquid pollutants from the system into the environment. On the other hand, the printed circuit board line of the present invention is clean and dry and is also relatively vapor free due to a noxious vapor removal subsystem which withdraws fumes from above the tanks and circulates the air through a scrubber prior to releasing it into the atmosphere. Additionally, the fluids and, in particular, the water based fluids are operated in a closed system. That is, all of the fluids which contain environmentally polluting ingredients are processed by a reverse osmosis system which recovers substantially all of the metal salts used in the plating operation and produces water which is virtually pure. The water is then suitable for reuse or for disposal in a manner which would not be permitted without the operation of the cleansing system and the metal salts recovered may be sold as scrap.
Finally, the plating system of the present invention reduces the quantity of "work in progress" due to the fact that the operation is continuous from raw stock to finished product. Conventional plating operations often have days to weeks of inventory work in progress which is being transferred from stage to stage in the plating and board manufacturing operation but which accounts for a substantial investment in inventory. The system of the invention is capable of producing finished printed circuit boards from start to finish in a total elapsed time of approximately six days rather than the several weeks of the prior art systems. The only queing of materials is at the head of the line as the material is placed into the continuous process. The continuous operation similarly reduces any backlog from a shutdown or delay in a specific operation in the sense that any holdup in the continuous operation is immediately flagged. For example, if a large quantity of materials stacks up at a particular inspection station, this alerts management to provide additional assistance at that particular station in order to guard against a delay or slowdown in the whole system due to difficulties encountered in one individual work station. In addition, the plating line of the present invention may be easily manned with relatively few employees. The only operations which are manually required are inspections which are made at specific fixed locations. The remainder of the operations of the system of the invention are under control by a computer or other automated production control facility.